A flow field of gas-solid two-phase flow consisting of air and sands (with grain size above 100 μm), and air and sand dusts (with grain size below 100 μm) is of common occurrence in desertification region. The former is mostly concentrated within the height less than 2 meters away from the ground, also referred to as surface wind drift sand flow (i.e., a form of soil wind erosion and desertification), and aggravates soil wind erosion and desertification accordingly. The latter mainly concerns sand dust storm within the height less than 10 meters away from the ground, and often leads to traffic stop, communication outage and air quality reduction, or even house and crop damage, loss of life and personal injury.
For example, about 1,325,600 persons in 19 counties of Gansu Province were hit by the sand dust storm on Apr. 24-25, 2010; crop damage area reached 206,800 hectares (ha). Though prevention and control or forecast of wind drift sand or sand dust storm has been studied for decades of years, and local treatment has achieved certain effect, the condition is severe on the whole: on one hand, the area of soil wind erosion and desertification continues to spread, the condition is more severe, and cultivated land area decreases. For example, a wind-sand disaster makes current area of desertification in Minqin area of Gansu Province which was an oasis 50 years ago reach about 94.5%. On the other hand, sand dust storm is still frequent; for example, Minqin area suffered 8 times of sand dust storm in 2010, and Riyadh (capital of Saudi Arabia) and Sydney in Australia in 2009, and the Phoenix of Arizona in the United States in 2011 respectively suffered the most severe sand dust storm over 20 years. It is thus clear that wind drift sand and sand dust storm has become an important environmental issue affecting human, economic and social development.
As pointed out by Balachandar et al. in an article of Annual Review of Fluid Mechanics: “Turbulence and multiphase flow are the two most challenging issues in fluid mechanics and it will be a more difficult challenge when combining the two”. Meanwhile, Marusic et al pointed out in a review article in 2010 that: “Recently, turbulence of wall boundary under high Reynolds number has gradually become a hot research field. There remain many challenges with regard to theory of such issue, scaling law, understanding of physical process, experimental technique, and numerical simulation.” Therefore, understanding and revealing of features and rules of wind drift sand flow or sand dust storm—turbulence of high Reynolds number of atmospheric boundary layer—will play a key role in accurate forecast of transport rate of wind drift sand flow and improvement of forecast model of sand dust storm, which reflects important application requirements, and will become an extremely complicated and challenging scientific issue.
However, with regard to study on wall turbulence of high Reynolds number (Re), understanding of basic issues such as concrete form of mean flow profile of wall turbulence, rule of turbulence fluctuation intensity change with Re, origin and scale of large scale structure outside and its spatial-temporal evolution rule, and existence of spectrum of “−1” power remains in dispute. Moreover, such basic theory issues concerning wall turbulence of high Re are highly relevant to forecast of transport rate of wind drift sand flow and improvement of forecast accuracy of sand dust storm. For example, value of Von Karman's constant and profile form will have direct influence on numerical calculation of wind drift sand flow or sand dust storm evolution process, but position in lower limit of mean flow profile may have influence on dust emission.
For study on turbulence of atmospheric boundary layer, there are issues such as short time of measurement of turbulence structure of atmospheric boundary layer, and unclear influence of factors including temperature stratification surface roughness and characteristics of incoming flow, etc. Therefore, it makes a lot of differences between the acquired results on one hand, and disputable understanding of basic issues such as universality of The Monin Obukhov theory, various anisotropic characteristics of fluctuation intensity, generation mechanism of coherent structure, as well as characterization of spectral of wind speed on the other hand. For the study on characteristics of wind drift sand flow or sand dust storm flow field, existing studies on exploration of relevance of wind drift sand flow and sand dust storm to turbulence structure are mostly speculative, especially for such extremely important issues on understanding and forecasting of wind drift sand flow or sand dust storm such as flow field characteristics and flow structure of wind drift sand flow or sand dust storm and interaction with dust emission and sand dust transport, it is hard for existing observation instruments and observation data to offer accurate answer, and it is unknown about whether existing conclusions, such as field observation conclusion of the University of Utah, can be introduced to flow field during wind drift sand flow or sand dust storm period.
It is thus clear that more effective field observation of flow field characteristics and structure of wind drift sand flow or sand dust storm of ground layer is necessary.
When realizing the present invention, the inventors found several defects of existing technology such as failure to measure three-dimensional structure of wall turbulence of high Reynolds number, failure to measure flow field characteristics of wind drift sand flow or sand dust storm, and failure to synchronize turbulence measurement with sand dust transport measurement, etc.